Influence of Polyester Chain Type in the Morphology of Silica-Carbon Composites Obtained by the Polymeric Precursor Method

Particulate composite materials containing metallic phase in ceramic matrices may be obtained by direct routes with the advantage of avoiding the partial collapse of the composite structure when a subsequent step for metal insertion is carried out. The non-metallic silica-carbon matrix combines high values of pore volume and surface area with chemical refractivity and may be applied as molecular sieves, adsorbents, filters and catalyst support. The Polymeric Precursor Method is a versatile method to obtain this composite type as the metal precursor can be reduced to metallic phase by pyrolysis of organic matter. In this work, it was used three different diol chain sizes obtaining silica-carbon composites through the pyrolysis of polyester precursor at 600°C for 3 hours in closed tubular oven. It was observed a direct dependence between the amorphous carbon phase amount and the polyester chain size. All of the composite samples presented dual distribution for mesopore size, situated at 3.8 and 11 nm in diameter. However, the pore volume and surface area significantly lowers for larger polyester chain sizes.

Download Full-text

Layered niobate KNb 3 O 8 synthesized by thepolymeric precursor method

Cerâmica ◽

10.1590/0366-69132018643692269 ◽

2018 ◽

Vol 64 (369) ◽

pp. 104-108 ◽

Cited By ~ 2

Author(s):

J. K. D. de Souza ◽

L. M. C. Honório ◽

J. M. Ferreira ◽

S. M. Torres ◽

I. M. G. Santos ◽

...

Keyword(s):

Solid State ◽

Surface Area ◽

Pore Volume ◽

Synthesis Method ◽

Total Pore Volume ◽

Polymeric Precursor Method ◽

Polymeric Precursor ◽

Precursor Method ◽

Solid State Method ◽

State Method

Abstract The polymeric precursor method was used for the synthesis of KNb3O8 and compared to the solid-state method. The materials were characterized by X-ray diffraction (XRD), infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and determination of surface area and total pore volume by nitrogen isotherms at 77 K. The material prepared by the polymeric precursor method was single-phase while K2Nb4O11 was obtained as secondary phase when the solid-state method was used, as evidenced by the XRD patterns and the Raman spectra. The morphology of the materials was significantly altered by the synthesis method, as the KNb3O8 prepared by the polymeric precursor method presented a more porous morphology leading to a higher surface area and pore volume.

Download Full-text

Influence of Oxidizing Atmosphere on Crystalline Phase Formation and Microstructural Properties of Mixed Cerium-Zinc Oxides Obtained by Polymeric Precursor Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.798-799.75 ◽

2014 ◽

Vol 798-799 ◽

pp. 75-78

Author(s):

L.L.M. Sales ◽

R.A. Candeia ◽

Fernando A.P. Cunha ◽

Jesana Moura Silva ◽

Alexsandra Cristina Chaves ◽

...

Keyword(s):

Surface Area ◽

Mixed Oxides ◽

Rietveld Method ◽

Xrd Analysis ◽

Polymeric Precursor Method ◽

Microstructural Properties ◽

Polymeric Precursor ◽

Precursor Method ◽

Oxidizing Atmosphere ◽

Catalytic Application

This paper presents the synthesis, characterization and influence of oxidizing atmosphere in the calcinations and sintering processes on microstructural properties of mixed oxides of Cerium and Zinc, obtained by the polymeric precursor method, aiming at a subsequent catalytic application. The material was submitted to calcinations and sintering at 900 and 1050 °C. The samples were characterized by XRD analysis techniques, surface area by BET method and refined by the Rietveld method. The results of X-ray diffraction showed that interest phase was formed, indicating that the method for obtaining the phase is effective. The results of surface area for the system calcined in air were 85 m2/g and 65 m2/g for the system subjected to oxidizing atmosphere both at 900°C, in the same temperature. It was observed that the temperature increase leads to an increase in crystallite size. This fact is in line with other studies in the literature.

Download Full-text

Morphological Analysis of the Amorphous Carbon Embedded Nickel-Silica Composite Submitted at Gradual Oxidation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.881.283 ◽

2016 ◽

Vol 881 ◽

pp. 283-288

Author(s):

Alberto Adriano Cavalheiro ◽

Graciele Vieira Barbosa ◽

Eliane Kujat Fischer ◽

Igor Silva de Sá ◽

Tiziana Azario de Medeiros ◽

...

Keyword(s):

Matrix Composite ◽

Amorphous Carbon ◽

Oxide Phase ◽

Metallic Nickel ◽

Composite Sample ◽

High Dispersion ◽

Polymeric Precursor Method ◽

Polymeric Precursor ◽

Carbon Phase ◽

Precursor Method

Amorphous embedded nickel-silica composites can be directly obtained by Polymeric Precursor Method when the polymeric precursor is pyrolysed in controlled atmosphere. The metallic particles dispersion into the matrix composite is very important to material applications, but the resistance against the oxidation under extreme conditions is also required. In this work, nickel-silica nanocomposite sample was synthesized for containing amorphous carbon as matrix interphase through the direct route based on the Polymeric Precursor Method. The composite sample was obtained by pyrolysis of polymeric precursor at 600 oC for 1 hour under nitrogen flow and then submitted to oxidation in oxygen flow at 400 oC up to 7 hours. It was observed by Transmission Electron Microscopy the metallic nickel nanoparticles present high dispersion into matrix composite. However, in spite of the border of the composite particles are easily oxidized and originate nickel oxide phase, as proven by X-Ray Diffraction, the amorphous carbon phase acts as protective phase for the majority of the composite sample. By Nitrogen Adsorption-Desorption Isotherms at 77 K it was demonstrated the carbon phase also preserves significantly the mesoporous nature of the composite under oxidation process.

Download Full-text